The present disclosure relates to a field bus network having two main users and at least one dependent user.
The disclosure lies in the field of real-time-capable redundant field bus networks having a ring topology such as e.g., SERCOS III. These are industrial networks which are used for networking industrial machines and are often based on Ethernet. Real-time-capable means that transmitted data reach or have reached the desired user at a definable time. In particular, it should be emphasized that conventional Ethernet networks, even if they are used for audio or video transmissions, are not real-time-capable since buffers are used here in order to compensate for data transmission delays or delayed or failed packets are simply discarded. In real-time-capable networks, in contrast, it can be guaranteed that each packet also reaches its target in time so that, especially in industrial machines, movements of different units also proceed synchronously. In particular, communication proceeds in fixed cycles, one packet being sent around by the main user in each cycle.
DE 10 2004 041 093 A1 describes such an annular network which, for example, could represent a control and drive system for industrial machines such as, e.g., shaftless introduction machines (i.e. without mechanical “shaft-type” coupling of the units). Such systems use an so-called contra rotating dual ring for the communication, between a main user (so-called “master”, e.g. an SPS) which controls the communication, and dependent users (so called “slaves” e.g. actuators and sensors) which receive commands and/or deliver data (especially measurement and diagnostic data) back to the master.
As described in EP 1 659 467 A1, it can be provided for reasons of redundancy that the dual ring breaks into two single rings in the case of a fault (e.g. in the case of a line interruption), between which the master is located. Communication between the master and all slaves can thus continue.
It is desirable to be able to continue to operate such a field bus network even in the case of a failure of a master.